There have been many attempts and approaches to increase the perceived realism of projected images. The simplest approaches involved merely color photography, larger screens, and more intense projection light sources. Later techniques included wide aspect ratio formats. Still later attempts involved curved screens of both cylindrical and spherical shape. In most curved screen projection techniques, the images are projected onto the concave side of the screen, although there have been systems in which the images are projected onto the convex side of curved screens.
One of the problems with projecting images onto curved screens is that the images are stored on flattened film such that distortions of the images occur in projecting them onto curved screens. One solution to this problem is to use multiple projectors to display portions of the total picture. However, there are complexities involved in seaming the image portions together to result in a continuous panorama. Another solution is to pre-distort the images as they are being recorded onto the film, or image sensor array in the case of video images, to compensate for the projection distortions.
In the field of curved screens, the majority have been cylindrical with some extending 360 degrees about the viewers' position. The majority of spherical screens have been less than entire spheres and have been illuminated with images projected onto the inner or concave surfaces of the screens. At least one known spherical screen is a single viewer hemispherical screen with the images rear screen projected onto the outer or convex side of the screen. One arrangement of a rear projected quasi-hemispherical screen for multiple viewers is known which is formed of a plurality of joined planar screens with a projector for each planar section.
In all the known spherical type screen arrangements, there are viewable nonprojected areas such that a viewer could turn in some direction and not see a portion of the projected images. As far as is known, there have been no spherical projection systems which completely surround a viewer such that, in any direction to which a viewer could turn, the viewer would see a portion of the screen.